When surfaces become contaminated with bacteria, fungi, yeasts, viruses, or other microorganisms, or “microbes,” sickness (morbidity) and, sometimes, death (mortality) may result. This is particularly true when surfaces in food processing plants and healthcare facilitates (e.g., hospitals) become contaminated with microorganisms.
In food processing plants, surfaces (e.g., solid surfaces, equipment surfaces, protective clothing, etc.) may become contaminated. Such contamination may be caused by or transferred to meat or other foods. In healthcare facilities, microbes may be released onto surfaces (e.g., solid surfaces, equipment surfaces, clothing, etc.) from infected individuals or otherwise. Once a surface becomes contaminated with microbes, contact with the contaminated surface may easily and readily transfer microbes to other locations, such as another surface, an individual, equipment, food, or the like.
As is well known, microbial contamination and transfer in certain environments may pose significant health risks. For example, the food that leaves a contaminated food processing plant will subsequently be eaten, and may cause sickness and, possibly, death. Microorganisms such as Listeria monocytogenes, Salmonella enteritidis, and Escherichia coli O157:H7 are of particular concern.
Microbial contamination is of concern in healthcare facilities since some of the patients of such facilities often suffer from infections by pathogenic microbes and, thus, bring the pathogenic microbes into such facilities. Further, many of those who are present in such facilities (e.g., patients) are sick and may be immunologically compromised. These individuals are, thus, at increased risk of becoming sick from infection by the contaminating microbes.
In view of the potential dangers of microbial contamination, in particular the ease with which microbes may be transferred in certain environments and the health hazards associated with the contamination of certain environments, a variety of techniques have been developed and employed to detect such contamination so that it may be promptly remedied.
Conventionally, environmental microbial testing includes obtaining a sample from a surface. This is typically done by contacting (e.g., wiping, swiping, etc.) the surface with a sterile sampling appliance, such as a swab or a sponge. Surfaces that are tested in this manner are usually quite clean; thus, the number of microorganisms that are picked up by the sampling appliance is typically quite low. Due to the small number of microorganisms, any microbes that are on (e.g., picked up by) the sampling appliance typically must be reproduced, or “grown” or “cultured,” to provide a sufficient number of organisms for further analysis. Accordingly, at least a portion of the sample is then typically neutralized and, optionally, stabilized, repaired, or enriched, then applied (e.g., transferring, swiping, dipping and agitating, etc.) to an appropriate growth media (e.g., agar (a gelatin or gelatin-like material), broth (a liquid), etc.), which includes nutrients that will help microbes of interest grow. The growth media may be selective, meaning that the growth media may include ingredients that will allow some microorganisms to grow at faster rates than other microbes or it may include ingredients that will prevent the growth of at least some undesired microbes. The growth media is incubated or held at a certain temperature for a predetermined period of time, typically about 24 to about 48 hours, or until microbial growth is visibly apparent.
Once the sample has had a sufficient opportunity to grow, the amount of bacteria (e.g., the number of colonies on an agar plate) that has grown may then be evaluated (e.g., by an individual or with automated equipment) to provide some indication of the number and type of microbes that were present on a certain area of the surface at the time the sample was taken-usually a day or two earlier. Immunological or other testing may also be performed to determine or confirm the identity or identities of any microbes of interest that were present in the sample.
For example, when testing for a Salmonella species of bacteria, a sample potentially including the Salmonella species may be applied to a selective growth media. The selective growth media may then be incubated for a period of about 24 to about 48 hours until growth of Salmonella microbes is visible. Once Salmonella colonies are visibly present on the selective growth media, the colonies may be evaluated to confirm their identities, and, optionally, counted to estimate a number of Salmonella microorganisms present on a certain area of the tested surface. Alternatively or additionally, the cultured microorganisms may be subjected to an immunoassay or nucleic acid assay to more directly confirm their identities.
Simpler, rapid, accurate tests for environmental organisms are needed. This invention provides devices and methods for such tests.